How to Implement Barcode and QR Code Scanning in Android Apps

Barcode and QR code scanning is a common feature in many Android apps, allowing users to quickly and easily scan codes to access information or perform specific actions. In this blog post, we will explore how to implement barcode and QR code scanning in Android apps using Kotlin and Java.

Getting Started

To begin with, we need to add the necessary dependencies to our project. Open the build.gradle file of your app module and add the following dependencies:

implementation 'androidx.appcompat:appcompat:1.3.0'
implementation 'com.google.zxing:core:3.4.0'
implementation 'com.journeyapps:zxing-android-embedded:4.2.0'

The appcompat library provides backward compatibility for different Android versions. The zxing-core library contains the core functionality of ZXing (pronounced “zebra crossing”) library that we will use for barcode and QR code scanning. Lastly, the zxing-android-embedded library integrates the ZXing library into our Android app.

Implementing Barcode and QR Code Scanning

1. Create a new activity, such as ScanActivity, that will handle the scanning functionality.

2. In the onCreate method of the activity, set the layout using setContentView(R.layout.activity_scan).

3. Add a SurfaceView to the layout file and apply its id as R.id.preview.

4. Create a method, such as initScanner, to initialize the barcode and QR code scanner. Inside this method, set up a CompoundBarcodeView by finding the reference with findViewById(R.id.preview). Initialize it by calling barcodeView.initializeFromIntent(intent).

5. Override the onResume method and call barcodeView.resume(). This will start the camera preview and begin scanning.

6. Override the onPause method and call barcodeView.pause(). This will stop the camera preview and release the resources.

7. Override the onActivityResult method and handle the result of the scanning process. You can retrieve the scanned barcode or QR code value using the Intent extra data.

8. Finally, call the initScanner method in the onCreate method to initialize the scanner.

Requesting Camera Permission

Before we can scan barcodes and QR codes, we need to request the camera permission from the user. You can add the following code snippets to simplify the process:

// Inside onCreate method of ScanActivity
if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
    != PackageManager.PERMISSION_GRANTED) {
    // Permission is not granted
    ActivityCompat.requestPermissions(this,
        arrayOf(Manifest.permission.CAMERA),
        CAMERA_PERMISSION_REQUEST)
} else {
    // Permission has already been granted
    initScanner()
}

// Override onRequestPermissionsResult method of ScanActivity
override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
    when (requestCode) {
        CAMERA_PERMISSION_REQUEST -> {
            if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // Permission has been granted
                initScanner()
            } else {
                // Permission has been denied
                Toast.makeText(this, "Camera permission required to scan barcodes", Toast.LENGTH_SHORT).show()
                finish()
            }
        }
    }
}

Summary

In this blog post, we have learned how to implement barcode and QR code scanning in Android apps using Kotlin and Java. We added the necessary dependencies, created a scan activity, initialized the barcode and QR code scanner, and handled the scanning result. We also discussed how to request the camera permission from the user. With this knowledge, you can now easily include barcode and QR code scanning functionality in your Android apps. Happy coding! 参考文献：

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